The mitotic kinesins are proteins that are involved in the mitotic spindle regulation, and play an essential role for progression of the mitotic phase in cell cycle. These proteins have a function of moving proteins along microtubules using the energy produced by ATP hydrolysis, and belong to a class of functional proteins generally called “molecular motors”. In the mitotic phase, the proteins are deeply involved in extension and maintenance of mitotic spindles, as well as formation of structure called spindle pole body, and further, they regulate progression of normal cell division through the movement of chromosomes along the spindle microtubules.
The mitotic kinesin Eg5 is one of the mitotic kinesins constituting an evolutionarily conserved subfamily. It is known that Eg5 has a function as a bipolar homotetramer molecule, and is involved in the formation of the bipolar spindle structure by crosslinking two of microtubules of the same direction and moving them in the direction toward the + (plus) end to cause sliding of two of the antiparallel microtubules, thereby keep − (minus) ends of microtubules at a distance and separate spindle pole bodies. The above functions of Eg5 were elucidated on the basis of the analysis of the human cells treated with anti-Eg5 antibody and a specific inhibitor [Cell, Vol. 83, p. 1159 (1995); J. Cell Biol., Vol. 150, p. 975 (2000); Jikken Igaku (Experimental Medicine), Vol. 17, p. 439 (1999)].
The gene of human Eg5 was cloned in 1995, and the expression of a full-length human Eg5 recombinant protein by using an insect cell and functional analysis using the resulting protein were reported [Cell, Vol. 83, p. 1159 (1995)]. The gene was registered in a public database as GenBank accession numbers: X85137, NM004523 and U37426. A biochemical analysis and structure analysis by crystallization of Eg5 utilizing an N-terminus portion of human Eg5, expressed by using Escherichia coli cells, were reported [J. Biological Chemistry, Vol. 276, p. 25496 (2001); Chemistry & Biology, Vol. 9, p. 989 (2002)], which applied a technique similar to the analysis utilizing Eg5 derived from Xenopus laevis having a high homology to the human Eg5 [Proc. Natl. Acad. Sci. USA, Vol. 96, p. 9106 (1999); Biochemistry, Vol. 35, p. 2365 (1996)].
As described above, the mitotic kinesin Eg5 is important as a target molecule of a novel mitotic phase acting agent and it is considered that an inhibitor against said molecule is promising as an agent for therapeutic treatment of diseases in which cell proliferation is involved (for example, restenosis, cardiac hypertrophy, arthritis, immunologic diseases, and the like) [WO01/98278; WO02/56880; WO02/57244; Trends in Cell Biology, Vol. 12, p. 585 (2002)].
As compounds having inhibitory activity against the human Eg5 enzyme, monastrol [Science, Vol. 286, p. 971 (1999)], quinazoline derivatives (WO01/98278), phenathiazine derivatives (WO02/57244), triphenylmethane derivatives (WO02/56880), dihydropyrimidine derivatives (WO02/79149; WO02/79169), dihydropyrazole derivatives (WO03/79973), and the like were reported.
Thiadiazoline derivatives having inhibitory activity against a transcription factor STAT6 activation or those having integrin antagonistic action are known (Japanese Patent Unexamined Publication (KOKAI) No. 2000-229959; WO01/56994), and further, those having an antibacterial activity, ACE inhibitory activity or the like are also known (WO93/22311; Japanese Patent Unexamined Publication (KOKAI) No. 62-53976; J. Bangladesh Chem. Soc., Vol. 5, p. 127 (1992)).